I work that route. I also ask that question : for a number of reasons, not least that people don't often know what they have purchased, and the question allows them to discover that the ticket that opened the barriers at Leeds will not open the barrier at Manchester, (because they need the second ticket to do so).
Also, because it's unsettling to scan 50 odd tickets to sowerby, and then see no one leave the train....
Same goes for Todmorden (common advance split point) and Walsden (off peak day return split point).
There are so many reasons for asking : the least of which is "2p".
I don't care how many, if any at all, tickets I scan.
I do care that my passenger load is looked after, and done in such a way that all bases are covered as best as I can.